Dear Sires,

Conditions and requirements:

-Code ASME Sec. VIII Div 1;
-Material SA 387/11 (Normalising + Tempering);
-Normalising 930°C/20 minutes;
-Tempering at 660°C/60 minutes;
-PWHT required, minimum 650°C, alternative PWHT temperature not permitted (Table UCS-56.1);
-PWHT temperature required by customer: 30°C minimum below the tempering temperature.

Question:

What is an acceptable solution?

Many thanks in advance

A. Paolocci

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paolocci

Probably you should have asked plate manufacturer to provide for tempering at temperature 680-690 °C for you to be able to perform PWHT at 650-660 °C.
You may propose your Client to accept repetition of mech.tests after PWHT to prove no decay occurred because of the PWHT at a temperature as high as the tempering temperature. If it were not for the peculiar requirement I wouldn't have any concern in making PWHT at temperature not higher than the tempering temperature.
You cannot skip Code requirement of PWHT at 650 C° minimun if you want to stamp the vessel. Your Client has to chose between Code stamping and PWHT temperature lower than 650 °C: both cannot stay together.
Mauro

Mr Gonzaga,
many thanks for your clear explanatory answer.
Paolocci

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paolocci

Hello
Why not skip the customers requirement of 30°C distance between tempering temperature and PWHT temperature? If after PWHT at 660°C sufficient mechanical properties are obtained, there is no technical reason that tempering should be 30°C higher.
Regards

Mr. Hockè

To clarify:

-Construction of pressure vessel using plates SA 387/11;
-Plates, at disposal, certified N + T with tempering temperature 660°C;
-Code requirement (UCS-56) minimum temperature for PWHT: 650°C;
-Customer requirement: PWHT at least 30°C minus that tempering temperature.

The question was: what is an acceptable solution for the manufacturer of pressure vessel ?

Thank you

A. Paolocci

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paolocci